1. Field of the Invention
The present invention relates to a gamma radiation field intensity meter, and more particularly to an electroscope-type dosimeter which is supplied a constant current from an energy source to provide rate of radiation dose rather than total accumulated dose.
2. Background of the Related Art
Electroscope-type dosimeters have been developed over the years to measure the accumulated or total dose of gamma radiation. Specifically, the prior art electroscope-type dosimeter determines the total gamma radiation exposed to it. Typically, the electroscope-type dosimeter, more commonly known as the Lauritsen electroscope, is precharged by a conventional dosimeter charger. The electroscope-type dosimeter includes a quartz fiber and a metal frame used as a charge acceptor, and during the charging process a potential is applied between the frame and the exterior of the dosimeter. Electrical charges of the same polarity appear on both the fiber and frame, causing the fiber to be repelled from the frame by a distance proportional to the applied voltage. The chamber walls or exterior of the electroscope-type dosimeter provides an electrostatic shield for the electroscope-type dosimeter. If the electroscope-type dosimeter is exposed to additional ionizing gamma radiation, the charge on the quartz fiber decreases and the fiber tends to return to the discharge position which is closer to the frame. An image of the fiber in the new position resulting from the additional gamma radiation is projected onto a reticle scale and viewed through an eyepiece lens of the dosimeter. The scale, typically calibrated in Milliroentgens or Roentgens, indicates total accumulated radiation dose, and may be read by looking through the eyepiece toward a lamp or other light source. Thus, the prior art electroscope-type dosimeters have been unable to measure the radiation dose rate experienced when exposed to an ionizing gamma radiation field.
It is, therefore, desirable to reliably measure the radiation dose rate which a meter is exposed to in a radiation field to further indicate whether the ionizing gamma radiation field is dangerous. In addition, it is also desirable that the gamma radiation field intensity meter be compact.